Whether it is mining engineering or rock engineering, the analysis of its slope stability is crucial. In order to better reflect the effect of unequal tension and pressure on rock and soil materials and intermediate principal stress effects or other effects, the unified strength theory is adopted. Considering the strength reduction factor, taking the seepage flow into account, the water migration is simulated by cellular automata, and the effects of its evolution rules and instability pattern on the stability of the rock slope are studied. It is converted into the expansion factor ws, the strength reduction factor Fs considering the unified strength theory is amended. The relationship between the intermediate principal shear stress parameter b and the stability safety factor is also analyzed, and the sensitivity of the parameters is analyzed. It is concluded that:

  1. The safety factor Fs increases with the increase of the intermediate principal shear stress parameter b.

  2. The CA simulation of the example shows that the stable safety factor first drops sharply, and then it shows irregular random fluctuations.


While the rapid development of infrastructure construction and resource development in Asia, especially in China, both mining and rock engineering have encountered critical issues related to the stability of rock slopes. Such as hydropower stations, high-speed railways, highways and mines, tailings dams, and so on… At the same time, many slope disasters such as collapses, landslides, etc. occur from time to time. A high-level landslide of approximately 100,000 cubic meters occurred in the village of Longxi Town, Wenchuan County, Sichuan Province, China on April 8, 2018[1]. In view of the effective work of the monitoring department, the unstable slope is predicted successfully, which cause no casualties. Therefore, the stability analysis of rock slope is the key to solve and control these rock mechanics problems.

The factors affecting slope stability include rock hardness, rock integrity, groundwater and rainfall, initial rock stress, construction methods and procedures, and earthquakes. The destructive mechanism coupled by different factors has not yet been reasonably analyzed. Therefore, although there are many methods for evaluating the stability of slopes, there is still no unified method for calculating the safety factor. In rock slope stability analysis, the choice of strength theory is also very important. Drucker-Prager yield criterion or Mohr-Coulomb strength theory is currently used. The former cannot represent the unequal tensile and compressive effects of geotechnical materials, while the latter cannot reflect the influence of intermediate principal stresses. In this paper, considering the use of unified strength theory[2–3] to calculate the safety factor of stability can make up for these deficiencies, give full play to the potential of geotechnical materials to resist damage, and more in line with the actual project.

In addition, when considering the influence of seepage on slope stability, there have been many studies on unsaturated slopes, but no systematic study on the effect of seepage on the stability of unsaturated rock slopes. The research on the unsaturated seepage of rock mass concentrates on the fractured rock mass[4–7], and the model or experimental study of slope rock mass[8–9] raises questions about the applicability of continuous media. In this paper, discrete cellular automata are used to simulate the seepage flow on the seepage surface, and the instability patterns are also discussed, as well as the stability safety factor. When setting up the initial conditions of simulation, we find that our assumptions of the initial water head field of unsaturated rock slope will have a great impact on the simulation results. Therefore, in the future research, the determination of the initial head field need carefully studied.

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